Castillo de San Marcos

Castillo de San Marcos is the oldest handmade national monument in the continental USA. The fort was built by the Spanish to protect their interests in the New World that later became known as America. Construction started in 1672 and ended in 1695. The fort is made of coquina stones. The unusual consistency of these compressed sea shells is the reason it remains standing to this day. The Monument site consists of 330 years of history and culture in an area of 20.5 acres.